An image formation device may include an attachable and detachable drum cartridge including a photoconductive drum. To the drum cartridge, a developer cartridge including a developer roller is removably attached.
A developer cartridge is formed with a supported member, which is supported by a supporting member provided to the drum cartridge. The developer cartridge includes an input gear and an electrode member. The input gear receives a rotation force from a drive gear provided to the device body of the image formation device. The electrode member is supplied a bias from a power supply member to a developer roller. The electrode member contacts the power supply member, provided to the device body, and then a bias is supplied from the power supply member to the electrode member.
By the supported member of the developer cartridge being supported by a supporting member of the drum cartridge, the developer cartridge is attached to the drum cartridge with a predetermined positioning, and the developer roller faces and contacts the photoconductive drum. When the developer cartridge and the drum cartridge are positioned in the device body, the input gear meshes with the drive gear, and the electrode member contacts the power supply member. When forming an image, a rotation force from the drive gear to the input gear is transmitted to the developer roller via a gear mechanism so that the developer roller is rotated. A bias from the power supply member is also transmitted to the developer roller via the electrode member. As such, toner is carried on the surface of the developer roller. Next, toner is transferred to the surface of the photoconductive drum so that an electrostatic latent image formed on the surface of the photoconductive drum is developed into a toner image. This toner image is transferred to a paper, which is provided between the photoconductive drum and a transfer roller. The toner transferred onto the paper is then fixed so that the image is formed on the paper.
One potential problem with a conventional configuration is that the positioning of the developer cartridge is unsteady. That is, when a rotational moment is applied to the developer cartridge in response to a rotation force from the drive gear to the input gear, a thrust force from the supported member to the supporting member is not balanced with a thrust force from the electrode member to the power supply member. This is at least one reason why the positioning of the developer cartridge is unsteady.